Electrodialysis apparatus having a vertical serpentine flow path



Dec. 27, 1 966 J. H. BROWN ETAL 3,294,671

ELECTRODIALYSIS APPARATUS HAVING A VERTICAL SERPENTINE FLOW PATH 5 Sheets-Sheet 1 Filed May 9, 1965 FIG. 2

1966 J H. BROWN ETAL 3, 94,

ELECTRODIALYS IS APPARATUS HAVING A VERTICAL SERPENTINE FLOW PATH Filed May 9. 1963 3 Sheets-Sheet 2 FIG. 3

IIIIIII/ k59 64 56 5.9

60 6/ JBK m o 0 o o a 72 74 66 FIG. 7

DAVID G CONNING B IJERRY H. BROWN 9.2 9/ 90 a9 ATTQRNEY Dec. 27, 1966 J. H. BROWN ETAL 3,

ELECTRODIALYSIS APPARATUS HAVING A VERTICAL SERPENTINE FLOW PATH Filed May 9, 1963 5 Sheets-Sheet 5 III/Q1 //7 FIG. :2

INVENTORS DAVID e. GONNING BJYERRYYH. BROWN ATTORNEY United States Patent 3,294,671 ELECTRODIALYSIS APPARATUS HAVING A VERTICAL SERPENTINE FLOW PATH Jerry Hugh Brown, Springdale, and David Guy Cunning, Stamford, Conn., assignors to American Machine & FoundryCompany, a corporation of New Jersey Filed May 9, 1963, Ser. No. 279,176 14 Claims. (Cl. 204-301) This invention relates in general to electrogravitational fluid treatment devices and, more particularly, to an electrogravitational device in which the product and waste streams are less subject to remixing.

An object of this invention is to provide an electrogravitational device in which a high degree of separation may be achieved in a single unit construction.

Another object of this invention is to provide a less costly and more easily fabricated electrogravitational apparatus to produce a very pure product stream from fluid passing through the apparatus. A further object of this invention is to provide an electrogravitational apparatus which may be used to separate a mixture in solution into some or all of its components, i.e. by fractionation.

This invention, provides an electrogravitational device having a container, electrode compartments containing electrodes at the extremities of the container and membranes within the container between the electrodes, the membranes extending at an angle from oppositely disposed walls of the container; the membranes extending from one wall extending between the membranes extending from the other wall, the membranes defining a serpentine flow path within the container, the container having outlet apertures withdrawing a product stream from the container, the outlet apertures being disposed in the container withinthe angle formed by the membranes and the opposite walls of the container from which the membranes extend.

Many objects, advantages and features of invention reside in the particular construction, combination and arrangement of parts involved in the embodiments of this invention and its practice as will be understood from the following description and accompanying drawing wherein:

FIGURE 1 is a longitudinal vertical section through an electrogravitational device with a central portion broken away according to a first embodiment of this in vention;

FIGURE 2 is a longitudinal vertical section through an electrogravitational device with a central portion broken away according to a second embodiment of this invention;

FIGURE 3 is a side view of an upper fragment of a piece of rigid plastic tubing cut to be fabricated into a third embodiment of this invention;

FIGURE 4 is a longitudinal vertical section through an electrogravitational device with a central portion broken away according to a third embodiment of this invention;

FIGURE 5 is a transverse vertical section through the rigid tube of FIGURE 3 showing a membrane inserted in a slot in the tube;

FIGURE 6 is a side view of a fragment of a piece of rigid plastic tubing cut to be fabricated into a modification of the third embodiment of this invention;

FIGURE 7 is a transverse section through a piece of tubing out according to FIGURE 6 showing pieces of membrane inserted through it;

FIGURE 8 is a longitudinal vertical section through a piece of tubing forming a container according to a modification of the third embodiment of this invention;

FIGURE 9 is a longitudinal vertical section through a fragment of a rectangular container containing a membrane folded to form a fourth embodiment of this invention;

FIGURE 10 is a longitudinal vertical section through a fragment of the top of a rectangular container containing a strip of membrane material arranged to form a fifth embodiment of this invention;

FIGURE 11 is a top view of the container shown in FIGURE 10; and

FIGURE 12 is a plan view of a strip of membrane material used in the fifth embodiment of this invention.

Referring to the drawing in detail, FIGURE 1 shows the generally rectangular container 10 having the two opposite walls 11 and 12 and the side walls 13. Membranes 15 and 14 are placed over the open upper and lower ends of container 10 and they are held in place by the electrode compartment forming top and bottom plates 16 and 17. Within the top and bottom plates 16 and 17 are disposed platinum wire mesh electrodes 18 and 19 which are connected by leads 20 and 21 to a suitable current source (not shown) so that electrode 18 functions as a cathode and electrode 19 functions as an anode. 'The tubes 22, 23, 24 and 25 conduct electrode washing streams past the electrodes 18 and 19.

Within the container 10 pairs of rods 26 and 27 extend between the side walls 13 to support stiff membrane plates 28 and 29 which extend at an angle upward from the walls 12 and 11, respectively. The membrane plates 28 and 29 extend completely between the walls 13 and butt against the Walls 11 and 12.

Concentrate stream drain tubes 30 extend through the wall 11 directly above the lower ends of the membrane plates 29 while concentrate stream drain tubes 31 extend through the wall 12 directly above the lower ends of the membrane plates 28. A valve 32 regulates the flow in each drain tube 30 and a valve 33 regulates the flow through each'drain tube 31. Inlet tube 34 leads through valve 35 into container 10 below the lowermost mem-' brane plate 29. A dilute stream outlet tube 36 leads out of container 10 above the uppermost membrane plate 29 through the flow regulating valve 37.

The first embodiment of this invention operates in the following manner. The membrane plates 28 and 29 are formed from cation permeable ion selective membrane material for example. Fluid to be treated, such as a salt solution, flows in-to container 10 through inlet tube 34 and describes a serpentine path definedby the membrane plates 28 and 29. Since electrode 19 functions as an anode and electrode 18 functions as a cathode, cations may be drawn upward through the cation permeable membranes 28 and 29. However, anions are drawn downward toward anode 19 and do not penetrate the ion selective cation permeable membranes 28 and 29 and so gather on the upper surfaces of the cation permeable membranes 28 and 29. Thus, as an example, if water was being desalted in this apparatus, a relatively dilute layer would be formed at the lower face and a more concentrated layer would be formed at the upper face of each membrane 28 and 29. The dilute layers, which are less dense because they have a lower salt concentration and a slightly higher temperature, rise along the lower surfaces of the sloping membrane sheets to flow from their upper ends and move upward. The more concentrated layers of salt solution on the upper surfaces of the membrane sheets slide down the rnem- [branes due to their higher density and are removed from compartment 10 through the drain tubes 30 and 31.

Since salt is removed at the lowermost membrane 29, fluid flowing upward past the second lowermost membrane 28 will be at a lower average salt concentration.

Further desalting of this water at the lowermost membrane 28 is then accomplished and more salt in solution is removed through the lowermost drain tube 31. The further diluted and desalted water passes to the next higher fluid treatment compartment defined between the membranes 28 and 2.9. In this way salt solution flowing upward through container becomes progressively more dilute as it rises within the electrogravitational device. As the fluid being treated passes above the uppermost membrane 28, it flows from container 10 through the product stream outlet tube 36 to give an exceptionally dilute product stream in one pass through the apparatus. The valves 35 and 37 control the flow into container 10 and the flow of the product stream from container 10. In a like manner, the valves 32 and 33 may be preset to give a desired flow through each of the outlet tubes 30 and 31.

If it is desired, a fairly tall container 10 may be used to separate a mixture of salts from solution. For example, a mixture of calcium, sodium and magnesium chloride in a water solution may be introduced through tube 34.

The ion with the highest transport number in a given system, which is a combination of the transport number in the given solution and the transport number through a given membrane sheet 28 or 29, will form a salt solution of a higher density above one of the lower membranes 28 or 29 to emerge from container 10 through one of the lower tubes 30 or 31. The ion with the next highest transport number will form a salt solution to emerge from the next higher tubes 30 and 31. Finally, the ion with the lowest transport number will form a salt solution to emerge from the highest tubes 30 and 31. Thus this apparatus may be used to achieve a high degree of separation of salts in solution by elect-rogravitation in successive effects in a manner not unlike fractional distillation.

Referring now to FIGURE 2, the second embodiment of this invention has a generally rectangular container 40 having the opposite walls 41 and 42 disposed between the side walls 43. The top and bottom ends of the container 40 are covered by membranes 14 and 15 which are held in place by the top and bottom electrode compartment forming plates 16 and 17 which are identical to those used in the first embodiment of the invention and which contain the electrodes 18 and 19 connected to the leads 20 and 21. Electrode washinlg stream tubes 22, 23, 24 and 25 lead in and out of the electrode compartment, forming top and bottom plates 16 and 17. Any suitable means (not shown) may be used to clamp the plates 16 and 17 in place over the membranes 14 and 15.

Extending downward at an angle from the wall 41 are plates of membrane material 45 which extend between the walls 43. Extending downward from the wall 42 between the walls 43 are the plates of membrane material 46 which extend between the membranes 45. The membranes 45 and 46 may :be glued, heat sealed, welded, clamped or otherwise held in place. Within the acute angles formed by the membranes 45 and 46 and the walls 41 and 42 are located dilute stream drain apertures 47 and 48. A jacket 49 surrounds the body of container 40 to receive the dilute stream flowing through the apertures 47 and 48. The dilute stream collects within jacket 49 and flows through tube 50 at .a rate of flow regulated by valve 51. A concentrate stream flows from container 40 through the lower tube 52 and valve 53 while fluid to be treated enters container 40 through tube 54 and valve 55.

The second embodiment of this invention may operate in the following manner. When it is desired to concentrate a salt solution, the salt solution enters container 40 through tube 54 having its rate of flow governed by valve 55. If the membranes 45 and 46 are cation permeable ion selective membranes, a salt solution of a greater concentration and 'density will form on the top surfaces of the membranes and flow downward following a serpentine path. At the same time, beneath each membrane a more dilute and less dense solution is formed. This solution rises beneath each membrane 45 and 46 to flow through a dilute stream drain aperture 47 or 48. Thus each successive lower fluid treatment compartment defined between a lower pair of membranes will have some less dense and less concentrated fluid Withdrawn from it through an aperture 47 or 48. Thus the apparatus shown for the second embodiment of this invention may be used to produce a very concentrated product flowing from the apparatus through tube 52 in one pass through the apparatus. The flow rate through tube 52 is regulated by valve 53 as the flow rate through the dilute stream d-rain apertures 47 and 48 is regulated by valve 51.

While cation permeable ion selective membranes have been shown in the first two embodiments of this invention, anion permeable ion selective membranes 28 and 29 or 45 and 46 may be used with the anodes 19 placed above and the cathodes 18 placed below the containers 10 and 40.

Referring now to FIGURES 3, 4 and 5, the third embodiment of this invention may be fabricated in cylindrical form. As shown in FIGURE 3, a length of stiff plastic tubing 56 has a number of angled cuts 57 and 58 made into each of its sides. As shown in FIGURE 5, pieces of membrane material 59 and 60 are inserted, respectively, in the cuts 57 and 58. The pieces of membrane 59 and 60 are then secured within the cylinder 56 and are trimmed away evenly beyond the outside of cylinder 56. Thus the tube 56 becomes a container 61 having the membranes 59 and 60 as a serpentine fluid flow path within it. If the container 61 is used to provide a dilute stream of relatively high purity, concentrate stream flow apertures 62 are formed in the cylinder 56 just above the places where the lowermost portions of the membranes 59 and 60 intersect the cylinder 56. A jacket 63 surrounds the container 61 to catch and collect concentrate from the drain apertures 62 so that the concentrate may pass from the apparatus through tube 64.

Fluid to be treated enters the apparatus through tube 65 while a very dilute stream flows from container 61 through tube 66. The end caps 67 and 68 hold the membranes 69 and 70 over the ends of the cylinder 56 and contain electrodes 71 and 72 which are connected to the leads 73 and 74. Electrode washing streams are conducted past electrodes 71 and 72 by tubes 75, 76, 77 and 78. The third embodiment of this invention may be used in the same manner which has been described for the first two embodiments.

FIGURES 6, 7 and 8 show a modification of the third embodiment of this invention in which the tube 56 has additional slots 80, 81, 82, 83, 84, 85, 86, 87 and 88 formed in it. Progressively narrower slots are formed above and parallel to each slot 57 and 58. As shown in FIGURES 7 and 8, membrane strips 89-96 are inserted through the slots 81-88. The membrane strips 89-96 are then trimmed beyond the cylinder 56 after being secured in position. The modification of the third embodiment of this invention thus makes use of groups of membranes rather than a single membrane within each stage.

FIGURE 9 shows a fourth embodiment of this invention using another method of construction. A rectangular container has two opposite walls 101 and 102 disposed between parallel walls 103. A sheet of relatively stiff and substantially self-supporting membrane material 104 is pleated or otherwise folded or formed into a zigzag shape. Membrane 104 is then placed within container 100 to extend between the walls 103 and have folds 105 extend upward at an angle from wall 102 while folds 106 extend upward at an angle from wall 101. Suitably placed fluid flow apertures 107 may be formed in walls 101 and 102 either directly above or below the points of contact of membrane 104 with walls 101 and 102. Fluid being treated flows through the main fluid flow apertures 108 to describe a serpentine path within container 100. If desired, membrane 104 may be fixed to the walls 101 and 102. The fourth embodiment of this invention may be used in the manner described.

As shown in FIGURES 10, 11 and 12, a fifth embodiment of this invention has a container 110 having the opposite walls 111 and 112 extending between the side walls 113. A number of rods 114 extend between the side walls 113 close to the walls 111 and 112 in a staggered line. Upper and lowermost rods 115 also extend between the side walls 113. One end of each rod 115 may extend beyond a wall 113 so that it may be rotated. A slot extends through each rod 115.

A thin strip of membrane material 116 is wound in a serpentine path about the rods 114 and fixed within the slots in the upper and lower rods 115. The rods 115 may then be rotated to draw the strip of membrane material 116 tightly about the rods 114 as shown in FIGURE 10. Suitable fluid flow apertures 117 are formed in the walls 111 and 112 either above or below the areas of the walls contacted by membrane 116. Rows of apertures 118 are formed in the strip of membrane material 116 to provide a serpentine path to be followed by the fluid to be treated.

Separate electrode compartments have been shown in the embodiments of this invention heretofore described. However, this invention may be modified and adapted for particular purposes. For example, a low salinity product water could be passed directly through the cathode compartment to limit scaling, or a platinum mesh cathode could be placed directly in low salinity product water at the stop of a stack in place of or in addition to the shown electrodes. In addition, while the membranes shown extending upward or downward from opposite sides of a container have been shown as being flat, curving the membranes upward or downward may help the electrogravitational separation in some cases. Multiple electrodes operating at different relative voltages may be used and ion exchange granules may be placed between the membranes.

What is claimed is:

1. In an electrogravitational device, a container having oppositely disposed first and second sides, electrodes in the top and bottom of said container, ion selective membranes in abutting relationship with and extending at an acute angle in substantially the same vertical direction from said first and second sides, said ion selective membranes extending from said first side extending between at least some of said ion selective membranes extending from said second side thereby defining a vertical serpentine flow path within said container, means for introducing fluid to be treated into said container, means for withdrawing a product stream from one end of said container, and means for withdrawing fluid from said container through the sides of said container within at least some of the acute angles formed by said ion selective membranes and the sides of said container.

2. An electrogravitational device comprising, in combination, a container having oppositely disposed first and second walls, electrodes in the top and bottom of said container, ion selective membranes in abutting relationship with and extending at an acute angle in the same vertical direction from said first and second walls, said ion selective membranes extending from said first wall extending between said ion selective membranes extending from said second wall thereby defining a vertical serpentine flow path within said container, means for introducing fluid to be treated into said container, means for withdrawing a product stream from one end of said container, and means for withdrawing fluid from said container through the oppositely disposed walls of said container within the acute angles formed by said ion selective membranes and the oppositely disposed walls of said container.

3. The combination according to claim 2 wherein said ion selective membranes extend upward at an acute angle from said first and second walls.

4. The combination according to claim 2 wherein said electrode in the top of said container is a cathode, said electrode in the bottom of said container is an anode, and said ion selective membranes are cation permeable.

5. The combination according to claim 3 wherein said container has sides between which said first and second walls extend and with the addition of pairs of rods extending betweenthe sides of said container, said ion selective membranes resting on said pairs of rods, extending between the sides of said container and butting with their lower ends against the walls of said container.

6. The combination according to claim 2 wherein said ion selective membranes extend downward at an acute angle from said first and second walls.

7. The combination according to claim 6 wherein said means for withdrawing a product stream from one end of said container withdraws a concentrate stream from the bottom of said container.

8. An electrogravitational device comprising, in combination, a container having oppositely disposed first and second sides, electrodes in the top and bottom of said container, ion selective membranes in abutting relationship with and extending at an acute angle in the same vertical direction from said first and second sides, said ion selective membranes from said first side extending between said ion selective membranes extending from said second side thereby defining a vertical serpentine flow path within said container, means for introducing fluid to be treated into said container, means for withdrawing a product stream from one end of said container, and means for withdrawing fluid from said container through the sides of said container within the acute angles formed by said ion selective membranes and the oppositely disposed sides of said container.

9. The combination according to claim 8 wherein said container has slots formed in its sides and said membranes are inserted in said slots.

10. The combination according to claim 8 with the addition of additional ion selective membranes extending across said container parallel to said membranes extending from said sides of said container, said additional membranes each extending between an adjacent membrane extending from the sides of said container and between the sides of said container.

11. An electrogravitational device comprising, in combination, a container having oppositely disposed walls, electrodes in the top and bottom of said container, ion selective membrane having folds extending upward in a zigzag path between said oppositely disposed walls, each fold extending at an acute angle from one of said oppositely disposed walls, said folds containing fluid flow apertures disposed in the same vertical direction at the ends of said folds, said membrane and said fluid flow apertures defining a vertical serpentine fluid treatment path within said container, means for introducing fluid to be treated into said container, and means for withdrawing fluid from said container through said oppositely disposed walls within the acute angles formed by the ends of each fold of said membrane disposed away from said fluid flow apertures and said oppositely disposed walls, and means for withdrawing a product stream from one end of said container.

12. The combination according to claim 11 with the addition of a staggered row of rods within said container extending across said container, said membrane extending about said rods forming said folds.

13. The combination according to claim 12 with the addition of upper and lower rotatably mounted rods, the ends of said membrane being secured to said rotatably mounted rods so that the rotation of said rotatably mounted rods tightens said membrane.

14. In an electrogravitational device, a container having oppositely disposed first and second sides, electrodes in the top and bottom of said container, ion selective membranes in abutting relationship with and extending at an acute angle in the same vertical direction from said first and second sides, said ion selective membranes extending from said first side extending between said ion selective membranes extending from said second side thereby defining a vertical serpentine flow path within said container, additional ion selective membranes extending across said container parallel to said membranes extending from the first and second sides of said container, said additional membranes each extending with a clearance between an adjacent membrane and the sides of said container, means for introducing fluid to be treated into said 15 container, means for withdrawing a product stream from References Cited by the Examiner UNITED STATES PATENTS 9/1958 Kollsman 204301 3/1962 Kollsman 204- 30 1 JOHN H. MACK, Primary Examiner.

E. ZAGARELLA, Assistant Examiner. 

1. IN AN ELECTROGRAVITATIONAL DEVICE, A CONTAINER HAVING OPPOSITELY DISPOSED FIRST AND SECOND SIDES, ELECTRODES IN THE TOP AND BOTTOM OF SAID CONTAINER, ION SELECTIVE MEMBERS IN ABUTTING RELATIONSHIP AND EXTENDING AT AN ACUTE ANGLE IN SUBSTANTIALLY THE SAME VERTICAL DIREACTION FROM FIRST AND SECOND SIDES, SAID ION SELECTIVE MEMBRANES EXTENDING FROM SAID FIRST SIDE EXTENDING BETWEEN AT LEAST ONE OF SAID ION SELECTIVE MEMBRANES EXTENDING FROM SAID SECOND SIDE THEREBY DEFINING A VERTICAL SERPENTINE FLOW PATH WITHIN SAID CONTAINER, MEANS FOR INTRODUCING FLUID TO BE TREATED INTO SAID CONTAINER, MEANS FOR WITHDRAWING A PRODUCT STREAM FROM ONE END OF SAID CONTAINER, AND MEANS FOR WITHDRAWING FLUID FROM SAID CONTAINER THROUGH THE SIDES OF SAID CONTAINER WITHIN AT LEAST SOME OF THE ACUTE ANGLES FORMED BY SAID ION SELECTIVE MEMBRANES AND THE SIDES OF SAID CONTAINER. 